Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia.
ARC Centre of Excellence for Translational Photosynthesis, Australia.
J Exp Bot. 2022 Mar 2;73(5):1546-1565. doi: 10.1093/jxb/erab477.
We compared how stomatal morphology and physiology control intrinsic leaf water use efficiency (iWUE) in two C3 and six C4 grasses grown at ambient (400 µmol mol-1) or glacial CO2 (180 µmol mol-1) and high (1000 µmol m-2 s-1) or low light intensity (200 µmol m-2 s-1). C4 grasses tended to have higher iWUE and CO2 assimilation rates, and lower stomatal conductance (gs), operational stomatal aperture (aop), and guard cell K+ influx rate relative to C3 grasses, while stomatal size (SS) and stomatal density (SD) did not vary according to the photosynthetic type. Overall, iWUE and gs depended most on aop and density of open stomata. In turn, aop correlated with K+ influx, stomatal opening speed on transition to high light, and SS. Species with higher SD had smaller and faster-opening stomata. Although C4 grasses operated with lower gs and aop at ambient CO2, they showed a greater potential to open stomata relative to maximal stomatal conductance (gmax), indicating heightened stomatal sensitivity and control. We uncovered promising links between aop, gs, iWUE, and K+ influx among C4 grasses, and differential K+ influx responses of C4 guard cells to low light, revealing molecular targets for improving iWUE in C4 crops.
我们比较了两种 C3 禾本科植物和六种 C4 禾本科植物在环境（400 µmol mol-1）或冰川 CO2（180 µmol mol-1）浓度、高光强（1000 µmol m-2 s-1）和低光强（200 µmol m-2 s-1）下的气孔形态和生理控制内在叶片水分利用效率（iWUE）的方式。与 C3 植物相比，C4 植物往往具有更高的 iWUE 和 CO2 同化速率，以及更低的气孔导度（gs）、操作气孔开度（aop）和保卫细胞 K+内流率，而气孔大小（SS）和气孔密度（SD）则不随光合作用类型而变化。总的来说，iWUE 和 gs 主要取决于 aop 和开放气孔的密度。反过来，aop 与 K+内流、向高光强过渡时的气孔开启速度和 SS 有关。具有较高 SD 的物种具有更小和开启速度更快的气孔。尽管 C4 植物在环境 CO2 浓度下具有较低的 gs 和 aop，但它们相对于最大气孔导度（gmax）表现出更大的气孔开启潜力，表明气孔敏感性和控制能力增强。我们发现 C4 禾本科植物之间的 aop、gs、iWUE 和 K+内流之间存在有希望的联系，以及 C4 保卫细胞对低光的不同 K+内流反应，揭示了提高 C4 作物 iWUE 的分子靶标。
